The MRI apparatus uses uniform magnetostatic field, and the magnetostatic field locally varies due to the magnetic susceptibility of an examinee. The effect of the local magnetic field variation appears as phase variation in image data. There is known an imaging method for emphasizing this phase variation through calculation processing (hereinafter referred to as susceptibility-emphasized imaging) (patent document 1). Attention has been paid to this susceptibility-emphasized imaging as an effective method to MR angiography of vein because the magnetic susceptibility can be emphasized based on deoxy hemoglobin in blood.
However, the susceptibility-emphasized imaging uses the phase variation caused by the magnetic susceptibility, and thus it requires an echo signal at the time point when about 70 ms elapses from the irradiation time of an RF pulse. Therefore, the repetitive time (TR) of a pulse sequence (hereinafter merely abbreviated as sequence) cannot be set to a short time, and thus the imaging time is increased.
Furthermore, a method of measuring plural echo signals with one RF pulse shot is known as a method of shortening the imaging time in the MRI apparatus, and an echo planar (EPI) method and a first spin echo (FSE) method are known as representative methods. An example of the susceptibility-emphasized imaging using the echo planar method to shorten the imaging time of the susceptibility-emphasized imaging is disclosed in (patent document 2).
Patent Document 1: U.S. Pat. No. 6,501,272
Patent Document 2: U.S. Pat. No. 7,154,269